The invention was made with government support under grant numbers 97308MI and 73054MI awarded by the National Institutes of Health. The Government has certain rights in these inventions.
The present invention relates to recombinant Newcastle disease virus RNA templates which may be used to express heterologous gene products in appropriate host cell systems and/or to construct recombinant viruses that express, package, and/or present the heterologous gene product. The expression products and chimeric viruses may advantageously be used in vaccine formulations. The present invention also relates to genetically engineered recombinant Newcastle disease viruses which contain modifications and/or mutations that make the recombinant virus suitable for use in vaccine formulations, such as an attenuated phenotype or enhanced immunogenicity.
The present invention relates to recombinant Newcastle disease viruses which induce interferon and related pathways. The present invention relates to the use of the recombinant Newcastle disease viruses and viral vectors against a broad range of pathogens and/or antigens, including tumor specific antigens. The invention is demonstrated by way of examples in which recombinant Newcastle disease virus RNA templates containing heterologous gene coding sequences in the negative-polarity were constructed. The invention further relates to the construction of recombinant Newcastle disease virus RNA templates containing heterologous gene coding sequences in the positive-polarity. Such heterologous gene sequences include sequences derived from a human immunodeficiency virus (HIV).
A number of DNA viruses have been genetically engineered to direct the expression of heterologous proteins in host cell systems (e.g., vaccinia virus, baculovirus, etc.). Recently, similar advances have been made with positive-strand RNA viruses (e.g., poliovirus). The expression products of these constructs, i.e., the heterologous gene product or the chimeric virus which expresses the heterologous gene product, are thought to be potentially useful in vaccine formulations (either subunit or whole virus vaccines). One drawback to the use of viruses such as vaccinia for constructing recombinant or chimeric viruses for use in vaccines is the lack of variation in its major epitopes. This lack of variability in the viral strains places strict limitations on the repeated use of chimeric vaccinia, in that multiple vaccinations will generate host-resistance to the strain so that the inoculated virus cannot infect the host. Inoculation of a resistant individual with chimeric vaccinia will, therefore, not induce immune stimulation.
By contrast, the negative-strand RNA viruse, would be attractive candidates for constructing chimeric viruses for use in vaccines. The negative-strand RNA virus, influenza, for example is desirable because its wide genetic variability allows for the construction of a vast repertoire of vaccine formulations which stimulate immunity without risk of developing a tolerance. Recently, construction of infectious recombinant or chimeric negative-strand RNA particles was achieved with the influenza virus (U.S. Pat. No. 5,166,057 to Palese et al., incorporated herein by reference in its entirety).
Virus families containing enveloped single-stranded RNA of the negative-sense genome are classified into groups having non-segmented genomes (Paramyxoviridae, Rhabdoviridae) or those having segmented genomes (Orthomyxoviridae, Bunyaviridae and Arenaviridae). The Paramyxoviridae family, described in detail below, and used in the examples herein, contain the viruses of Newcastle disease virus (NDV), parainfluenza virus, Sendai virus, simian virus 5, and mumps virus.
The Newcastle disease Virus is an enveloped virus containing a linear, single-strand, nonsegmented, negative sense RNA genome. The genomic RNA contains genes in the order of 3xe2x80x2-NP-P-M-F-HN-L, described in further detail below. The genomic RNA also contains a leader sequence at the 3xe2x80x2 end.
The structural elements of the virion include the virus envelope which is a lipid bilayer derived from the cell plasma membrane. The glycoprotein, hemagglutinin-neuraminidase (HN), protrudes from the envelope allowing the virus to contain both hemagglutinin and neuraminidase activities. The fusion glycoprotein (F), which also interacts with the viral membrane, is first produced as an inactive precursor, then cleaved post-translationally to produce two disulfide linked polypeptides. The active F protein is involved in penetration of NDV into host cells by facilitating fusion of the viral envelope with the host cell plasma membrane. The matrix protein (M), is involved with viral assembly, and interacts with both the viral membrane as well as the nucleocapsid proteins.
The main protein subunit of the nucleocapsid is the nucleocapsid protein (NP) which confers helical symmetry on the capsid. In association with the nucleocapsid are the P and L proteins. The phosphoprotein (P), which is subject to phosphorylation, is thought to play a regulatory role in transcription, and may also be involved in methylation, phosphorylation and polyadenylation. The L gene, which encodes an RNA-dependent RNA polymerase, is required for viral RNA synthesis together with the P protein. The L protein, which takes up nearly half of the coding capacity of the viral genome is the largest of the viral proteins, and plays an important role in both transcription and replication.
The replication of all negative-strand RNA viruses, including NDV, is complicated by the absence of cellular machinery required to replicate RNA. Additionally, the negative-strand genome can not be translated directly into protein, but must first be transcribed into a positive-strand (mRNA) copy. Therefore, upon entry into a host cell, the genomic RNA alone cannot synthesize the required RNA-dependent RNA polymerase. The L, P and NP proteins must enter the cell along with the genome on infection.
It is hypothesized that most or all of the viral proteins that transcribe NDV mRNA also carry out their replication. The mechanism that regulates the alternative uses (i.e., transcription or replication) of the same complement of proteins has not been clearly identified but appears to involve the abundance of free forms of one or more of the nucleocapsid proteins, in particular, the NP. Directly following penetration of the virus, transcription is initiated by the L protein using the negative-sense RNA in the nucleocapsid as a template. Viral RNA synthesis is regulated such that it produces monocistronic mRNAs during transcription.
Following transcription, virus genome replication is the second essential event in infection by negative-strand RNA viruses. As with other negative-strand RNA viruses, virus genome replication in Newcastle disease virus (NDV) is mediated by virus-specified proteins. The first products of replicative RNA synthesis are complementary copies (i.e., plus-polarity) of NDV genome RNA (cRNA). These plus-stranded copies (anti-genomes) differ from the plus-strand mRNA transcripts in the structure of their termini. Unlike the mRNA transcripts, the anti-genomic cRNAs are not capped and methylated at the 5xe2x80x2 termini, and are not truncated and polyadenylated at the 3xe2x80x2 termini. The cRNAs are coterminal with their negative strand templates and contain all the genetic information in each genomic RNA segment in the complementary form. The cRNAs serve as templates for the synthesis of NDV negative-strand viral genomes (vRNAs).
Both the NDV negative strand genomes (vRNAs) and antigenomes (cRNAs) are encapsidated by nucleocapsid proteins; the only unencapsidated RNA species are virus mRNAs. For NDV, the cytoplasm is the site of virus RNA replication, just as it is the site for transcription. Assembly of the viral components appears to take place at the host cell plasma membrane and mature virus is released by budding.
The RNA-directed RNA polymerases of animal viruses have been extensively studied with regard to many aspects of protein structure and reaction conditions. However, the elements of the template RNA which promote optimal expression by the polymerase could only be studied by inference using existing viral RNA sequences. This promoter analysis is of interest since it is unknown how a viral polymerase recognizes specific viral RNAs from among the many host-encoded RNAs found in an infected cell.
Animal viruses containing plus-sense genome RNA can be replicated when plasmid-derived RNA is introduced into cells by transfection (for example, Racaniello et al., 1981, Science 214:916-919; Levis, et al., 1986, Cell 44: 137-145). In the case of poliovirus, the purified polymerase will replicate a genome RNA in in vitro reactions and when this plus-sense RNA preparation is transfected into cells it is infectious (Kaplan, et al., 1985, Proc. Natl. Acad. Sci. USA 82:8424-8428). However, the template elements which serve as transcription promoter for the poliovirus-encoded polymerase are unknown since even RNA homopolymers can be copied (Ward, et al., 1988, J. Virol. 62: 558-562). SP6 transcripts have also been used to produce model defective interfering (DI) RNAs for the Sindbis viral genome. When the RNA is introduced into infected cells, it is replicated and packaged. The RNA sequences which were responsible for both recognition by the Sindbis viral polymerase and packaging of the genome into virus particles were shown to be within 162 nucleotides (nt) of the 5xe2x80x2 terminus and 19 nt of the 3xe2x80x2 terminus of the genome (Levis, et al., 1986, Cell 44: 137-145). In the case of brome mosaic virus (BMV), a positive strand RNA plant virus, SP6 transcripts have been used to identify the promoter as a 134 nt tRNA-like 3xe2x80x2 terminus (Dreher, and Hall, 1988, J. Mol. Biol. 201: 31-40). Polymerase recognition and synthesis were shown to be dependent on both sequence and secondary structural features (Dreher, et al., 1984, Nature 311: 171-175).
The negative-sense RNA viruses have been refractory to study of the sequence requirements of the replicase. The purified polymerase of vesicular stomatitis virus is only active in transcription when virus-derived ribonucleoprotein complexes (RNPs) are included as template (De and Baneijee, 1985, Biochem. Biophys. Res. Commun. 126: 40-49; Emerson and Yu, 1975, J. Virol. 15: 1348-1356; Naito and Ishihama, 1976, J. Biol. Chem. 251: 4307-4314). With regard to influenza viruses, it was reported that naked RNA purified from virus was used to reconstitute RNPs. The viral nucleocapsid and polymerase proteins were gel-purified and renatured on the viral RNA using thioredoxin (Szewczyk, et al., 1988, Proc. Natl. Acad. Sci. USA, 85: 7907-7911). However, these authors did not show that the activity of the preparation was specific for influenza viral RNA, nor did they analyze the signals which promote transcription.
Only recently has it been possible to recover negative strand RNA viruses using a recombinant reverse genetics approach (U.S. Pat. No. 5,166,057 to Palese et al.). Although this method was originally applied to engineer influenza viral genomes (Luytjes et al. 1989, Cell 59: 1107-1113; Enami et al. 1990, Proc. Natl. Acad Sci. USA 92: 11563-11567), it has been successfully applied to a wide variety of segmented and nonsegmented negative strand RNA viruses, including rabies (Schnell et al. 1994, EMBO J. 13:4195-4203); respiratory syncytial virus (Collins et al. 1991, Proc. Natl. Acad. Sci. USA 88:9663-9667); and Sendai virus (Park et al. 1991, Proc. Natl. Acad. Sci. USA 88:5537-5541; Kato et al., 1996, Genes Cells 1:569-579). However, this approach has yet to be applied to Newcastle disease virus RNA genomes.
Recombinant Newcastle disease viral RNA templates are described which may be used with RNA-directed RNA polymerase to express heterologous gene products in appropriate host cells and/or to rescue the heterologous gene in virus particles. In one embodiment, the invention relates to recombinant Newcastle disease viruses which induce interferon and related pathways. The present invention relates to recombinant Newcastle disease viruses which contain modifications which result in phenotypes which make the recombinant virus more suitable for use in vaccine formulations, e.g., attenuated phenotypes and enhanced immunogenicity. In another embodiment, the present invention relates to engineering recombinant Newcastle disease viruses and viral vectors which contain heterologous genes including genes of other viruses, pathogens, cellular genes, tumor antigens etc.
In another embodiment, the present invention relates to engineering recombinant Newcastle disease viruses and viral vectors for the use as vaccines. The present invention relates to vaccine formulations suitable for administration to humans, as well as veterinary uses. The vaccines of the present invention may be designed for administration to domestic animals, including cats and dogs; wild animals, including foxes and racoons; livestock and fowl, including horses, cattle, sheep, turkeys and chickens.
In yet another embodiment, the invention relates to recombinant Newcastle disease viral vectors and viruses which are engineered to encode mutant Newcastle disease viral genes or to encode combinations of genes from different strains of Newcastle disease virus. The RNA templates of the present are prepared by transcription of appropriate DNA sequences with a DNA-directed RNA polymerase. The resulting RNA templates are of the negative-polarity and contain appropriate terminal sequences which enable the viral RNA-synthesizing apparatus to recognize the template. Alternatively, positive-polarity RNA templates which contain appropriate terminal sequences which enable the viral RNA-synthesizing apparatus to recognize the template, may also be used. Expression from positive polarity RNA templates may be achieved by transfection of plasmids having promoters which are recognized by the DNA-dependent RNA polymerase. For example, plasmid DNA encloding positive RNA templates under the control of a T7 promoter can be used in combination with the vaccinia virus T7 system.
Bicistronic mRNAs can be constructed to permit internal initiation of translation of viral sequences and allow for the expression of foreign protein coding sequences from the regular terminal initiation site, or vice versa. Alternatively, a foreign protein may be expressed from internal transcriptional unit in which the transcriptional unit has an initiation site and polyadenylation site. In another embodiment, the foreign gene is inserted into an NDV gene such that the resulting expressed protein is a fusion protein.
The recombinant mutant Newcastle disease viral RNA templates of the present invention may be used to transfect transformed cell lines that express the RNA dependent RNA-polymerase and allow for complementation. Alternatively, a plasmid expressing from an appropriate promoter, can be used for virus specific (chimeric) RNA transfection. Complementation may also be achieved with the use of a helper virus which provides the RNA dependent RNA-polymerase. Additionally, a non-virus dependent replication system for Newcastle disease virus is also described. The minimum subset of Newcastle disease virus proteins needed for specific replication and expression of the virus are the three proteins, L, P and NP, which can be expressed from plasmids by a vaccinia virus T7 system. In yet another embodiment, when plasmids encoding the antigenomic copy of the NDV genome are used to supply the viral genome, the minimum subset of Newcastle disease virus proteins needed for specific replication and expression of the virus are the L and P proteins. When the antigenomic copy of the NDV genome is transcribed, th NP polymerase protein is the first protein transcribed, thus it is not necessary to additionally provide the NP polymerase in trans.
The expression products and/or chimeric virions obtained may advantageously be utilized in vaccine formulations. The expression products and chimeric virions of the present invention may be engineered to create vaccines against a broad range of pathogens, including viral antigens, tumor antigens and auto antigens involved in autoimmune disorders. In particular, the chimeric virions of the present invention may be engineered to create anti-HIV vaccines, wherein an immunogenic polypeptide from gp160, and/or from internal proteins of HIV is engineered into the glycoprotein HN protein to construct a vaccine that is able to elicit both vertebrate humoral and cell-mediated immune responses. The use of recombinant Newcastle disease virus for this purpose is especially attractive since Newcastle disease virus is not pathogenic in humans. The use of recombinant Newcastle disease virus for delivering tumor antigens is particularly attractive given the known antineoplastic and immunopotentiating properties of the virus.
As used herein, the following terms will have the meanings indicated:
cRNA=anti-genomic RNA
HIV=human immunodeficiency virus
L=large protein
M=matrix protein (lines inside of envelope)
MDCK=Madin Darby canine kidney cells
MDBK=Madin Darby bovine kidney cells
moi=multiplicity of infection
NA=neuraminidase (envelope glycoprotein)
NDV=Newcastle disease Virus
NP=nucleoprotein (associated with RNA and required for polymerase activity)
NS=nonstructural protein (function unknown)
nt=nucleotide
PA, PB1, PB2=RNA-directed RNA polymerase components
RNP=ribonucleoprotein
rRNP=recombinant RNP
vRNA=genomic virus RNA
WSN=influenza A/WSN/33 virus
WSN-HK virus: reassortment virus containing seven genes from WSN virus and the NA gene from influenza A/HK/8/68 virus